1. Field of the Invention
The present invention relates to a component mounting apparatus, more specifically to one having a plurality of vacuum pick-up nozzles which are mounted on a mounting head to revolve about a supporting shaft, wherein the vacuum pick-up nozzles are moved to a location as operated by an actuator mounted on a designated location in the direction of revolution, thereby making a forward movement of the vacuum pick-up nozzles by the actuator in order to perform pick-up and/or mounting a component.
2. Description of Related Art
For making electronic circuits by mounting components on a circuit board, a mounting machine is widely used. The mounting machine is provided with a vacuum pick-up nozzle that picks up a component and is moved in the directions of the X axis and Y axis relative to the circuit board to the designated location above the mounting position on the circuit board. Subsequently, the vacuum pick-up nozzle is made to descend toward the circuit board for mounting the component on the designated position on the circuit board.
Conventionally, large and high speed machines so-called rotary machines were the mainstream. However, in recent years, such rotary machines are losing popularity because they are large and expensive and thus compact machines having movable mounting heads are the mainstream now. In compact mounting machines of a type having a movable head for mounting small components such as chip or the like, it is typical that a single tool head has a plurality of nozzles in the order of, for example 4 to 12 in order to improve productivity by shortening the tact time. Such mounting machines are known as cell type mounting machines.
The mounting machines having a plurality of nozzles on the tool head are further classified into two kinds. One is a type having only a single actuator at one point in the direction of revolution for moving the vacuum pick-up nozzles up and down, thereby performing a vacuum pick-up and mounting operation by revolving the nozzles below the actuator. The other is a type having the nozzles fixed to the tool head rather than revolving in the direction of circumference and an actuator is provided for each nozzle for moving up and down.
The first type as mentioned hereinabove is advantageous in that the amount of movement of the head is small and a sufficiently powerful actuator can be used because only one actuator is used for moving the nozzles up and down in the case of continuous pick-up from a single cassette or mounting chips adjacent to one another with a small pitch. Accordingly, since the up and down stroke time of the nozzles can be reduced, capacity per tool head can be enhanced. Such type of mounting machines is known as a cell type middle speed machine. Such mounting machines are disclosed, for example in Japanese Patent Application Publication No. HEI 9-191488 and Japanese Patent Application Publication No. 2001-223498.
In the case of a revolving tool head having a plurality of vacuum pick-up nozzles along the circumference, a large number of nozzles move at a high speed in the circumferential direction about the axis of revolution and make the down-stroke by the push-down of a lever of the abovementioned actuator at the time when they come below the actuator. It is to be noted that the lever can simply push down, and the up-stroke of the nozzles depends on a restoration force of a spring as the lever moves up. Let the revolving moving time of the nozzle in the circumferential direction within the tool head and the moving time of the nozzles in the up and down direction be T1 and T2, respectively, and the numerical value to be the basis of the tact time of the mounting machine is T1+T2. Since T1 and T2 are the numerical numbers that are to be minimized as much as possible under various restricted conditions, each value may have a certain room to be reduced but T1+T2 is the basis of the tact time, which is the limitation of the conventional mounting machines.
However, in the case of a revolving tool head, there is, for example a 14 mm stroke for up and down movement of the nozzles. In the case of picking up and mounting a small chip of about 2 mm in component height, the nozzles are mostly required to be moved with proper alignment only about 3 mm near the bottom end of the up and down stroke. In other words, there is no problem in principle if the nozzles may simultaneously move and go up and down during a 14−3=11 mm stroke. This means that the T1+T2−(the time of the simultaneous movement) can be the basis of the tact time. Unfortunately, however, the reality is to set the time of the simultaneous movement to essentially zero due to friction and mechanical interference, thereby restricting the reduction of the tact time in conventional mounting machines.
(Reference patent document 1) Japanese Patent Application Publication No. HEI 9-181488
(Reference patent document 2) Japanese Patent-Application Publication No. 2001-223498
(Reference patent document 3) Japanese Patent-Application Publication No. 2000-114788
(Reference patent document 4) Japanese Patent-Application Publication No. HEI 2-99000
(Reference patent document 5) Japanese Patent-Application Publication No. HEI-2-194700